Lead/acid batteries, behavior

Lead dioxide has been the subject of study as an anode material from the early days of electrocatalysis due, in large part, to its importance in the lead-acid battery. Its good corrosion resistance at high anodic potentials has also resulted in its use in a number of other electrochemical processes, e.g. organic synthesis (see Sect. 8). Aspects of the anodic behavior of Pb02 have been relatively recently reviewed by Randle and Kuhn [320], In acid solution, / -Pb02 has been shown to exhibit a Tafel slope of ca. 120 mV decade -1... 

About 40Z of the world s lead production goes into the manufacture of the lead acid battery, and it is by far the dominant technology in rechargeable battery systems with market size of about 12 billion. The earliest reference on this battery is from 1854 (5), while the real commercial breakthrough came with Plante s experiments in 1859(4). Gaston Plante had been investigating the effect of polarization on different metals and he noticed the unique behavior of lead plates in dilute sulphuric acid as the electrolyte, and the rest is history. 

Valve-regulated lead-acid batteries are used today in almost all applications which are applicable for conventional lead acid batteries. Since these batteries generation was basically for portable batteries, this is still a market today, for instance in the medical area. Larger types, which were developed about 20 years ago, have a wide field in military applications. Since the 1980s modern tanks and military shelters have been equipped with the 123-V 100-Ah NATO type. Its advantage besides the high deep discharge ability is the maintenance-free behavior, especially due to the limited space conditions in modern tanks. 

Rechargeable elements trace back to Johann Wilhelm Ritter, while the invention of the lead-acid battery is attached to such famous names as Gaston Plante, Camille Faure, Henry Tudor, and Volkmar. The industrial production began over 100 years ago and it demonstrates the difficulty implemented in electrochemical elements that even today sometimes the behavior of a battery can t be foreseen or explained totally. On the field of maintenance-free lead-acid batteries Otto Jache made a break-through in 1957 after extensive preparatory work by many others. 

This approach has been used to model the behavior of several different types of battery systems, including a recent study by Lafollette (25) of a very high-rate lead-acid battery. An important conclusion of this work was that for thin electrodes, operated at very high rates, electrolyte depletion at the pore wall is very significant, a factor not usually considered in more conventional battery situations in which the actual interfacial current densities are not particularly high. 

The efficiency factor of a discharging battery is expressed by the Peukert s law. W. Peukert, a German scientist (1897), devised a formula expressing loss at a given discharge rate in Peukert numbers. Because of the sluggish behavior of lead acid, Peukert numbers apply mostly to this chemistry. They help to calculate the capacity under various load conditions. 

FIG U RE 8.2 Typical discharge curves of lead acid as a function of C-rate. Smaller batteries are rated at a 1C discharge rate. Due to sluggish behavior, lead acid is rated at 0.2 C (5 h) and 0.05 C (20 h). 

Although the motion of protons does not lead to electrical conduction in the case of benzoic acid, electronic and even ionic conductivity can be found in other molecular crystals. A well-studied example of ionic conduction is a film of polyethylene oxide (PEO) which forms complex structures if one adds alkaline halides (AX). Its ionic conductivity compares with that of normal inorganic ionic conductors (log [cr (Q cm)] -2.5). Other polymers with EO-units show a similar behavior when they are doped with salts. Lithium batteries have been built with this type of... 

---